Process for bleaching goods during drycleaning

ABSTRACT

The addition of a mixture of alkali metal sulfite and thiosulfate to a drycleaning solvent containing a bleaching agent destroys any excess bleaching agent, thus preventing degradation of the textile fabric being drycleaned, without detrimental side effects.

United States Patent 1 1111 3,859,044

Blomfield 1 1 Jan. 7, 1975 [54] PROCESS FOR BLEACHING GOODS 3,679,590 7/1972 Cormany ct a1. 8/142 X DURING DRYCLEANING 3,726,800 4/1973 Yelin et a1. 8/111 X [75] lnventor: Rodney A. Blomfield, Painesville,

Ohio

[73] Assignee: Diamond Shamrock Corporation,

Cleveland, Ohio [22] Filed: Sept. 27, 1972 [21] Appl. No.: 292,538

[52] US. Cl. 8/142, 8/111 [51] Int. Cl D061 l/22 [58] Field of Search 8/111, 142

[56] References Cited UNITED STATES PATENTS 3,635,667 1/1972 Keay et a1 8/142 Primary ExaminerLeland A. Sebastian Attorney, Agent, or FirmWilliam A. Skinner [57] ABSTRACT The addition of a mixture of alkali metal sulfite and thiosulfate to a drycleaning solvent containing a bleaching agent destroys any excess bleaching agent, thus preventing degradation of the textile fabric being drycleaned, without detrimental side effects.

4 Claims, No Drawings PROCESS FOR BLEACHING GOODS DURING DRYCLEANING BACKGROUND OF THE INVENTION Drycleaning is rapidly gaining in popularity as a method of cleaning textile fabrics. The currently employed systems, however, generally consisting of a drycleaning solvent, detergent, and small amounts of water, are for the most part incapable of removing oxidizable stains, such as those from ketchup, soft drinks, jelly, tea, medicines, and the like, from textile fabrics.

It has been reported that such stains may be successfully removed by the addition of various bleaching agents to the drycleaning bath. While the stain problem is thus overcome, it has been noted that the fabrics so treated exhibit excessive losses of strength upon repeated cleaning, apparently due to the retention by the fabrics of excess bleaching agent. Another problem results from the practice of reclaiming the soilcontaminated drycleaning solvent by fractional distillation wherein the heavy residues remain in the pot. Obviously, the combination of oxidizing agent with organic soils and detergents at the elevated temperatures involved constitutes a serious hazard.

STATEMENT OF THE INVENTION Therefore, it is an object of the present invention to provide a method of bleaching textile fabrics without degradation of said fabrics or potential operating hazards.

It is a further object of the present invention to provide a method for neutralizing the excess oxidizing agent employed in a drycleaning/bleaching operation efficiently and without side effects.

These and further objects of the present invention will become apparent to those skilled in the art from the specification and claims which follow.

There has now been found an improvement in the method for bleaching textile fabrics in a drycleaning solvent having emulsified therein an oxidizing agent capable of effecting the desired bleaching, which improvement consists essentially of adding to said solvent, subsequent to the completion of the desired bleaching reaction but prior to removal of the solvent from the textile fabric, a mixture of alkali metal sulfite and thiosulfate, the sulfite constituting from 50 to 95 percent by weight of the sulfite/thiosulfate and the amount of said mixture used being at least that sufficient to react with the remaining oxidizing agent in the solvent.

By this means, the bleaching operation may be allowed to proceed to the desired extent, following which the excess oxidizing agent may be completely and efficiently neutralized, thus eliminating the problem of subsequent fabric degradation and avoiding any potential for uncontrolled oxidation in the sump of the drycleaning solvent reclamation still. At the same time, no detrimental side effects, such as odor on or discoloration of the fabric are evidenced.

DESCRIPTION OF THE PREFERRED EMBODIMENTS By the use of the term drycleaning solvent, it is intended to refer to those materials commonly employed for this purpose such as trichloroethylene, perchloroethylene, Stoddard solvent, and the various chlorofluoro organics, e.g., trichlorotrifluoroethane. In a normal drycleaning system (i.e., solvent-detergent-waterbleach-etc.) such solvent will constitute from 88 to 98 percent by volume.

In order to emulsify the generally aqueous bleaching agent into the solvent, any number of surfactant materials may be used. Since, in order to reduce the oxidizable materials present to a minimum, the bleaching step is generally preceded by a cleaning operation, it is generally convenient to employ the same detergent composition used in the cleaning step as the emulsifier. These drycleaning detergents are usually multicomponent proprietary mixtures of anionic, cationic and/or nonionic surfactants. Exemplary are:

A. high molecular weight alkanolamides, typically the reaction product of an alkanolamine such as monoor diethanolamine with a fatty acid or ester having an alkyl residue of from eight 20 carbon atoms such as lauric or stearic acid;

B. alkali metal or ammonium salts of high molecular weight alkyl sulfate and sulfonates, the alkyl radical having at least 8 and preferably in excess of l2 and up to 22 carbon atoms, such as sodium lauryl sulfate and ammonium cetyl sulfonate; I

C. salts of alkylbenzene sulfonic acids, the alkyl radical typically having from eight 20 carbons, such as the amine salt of linear dodecylbenzenesulfonic acid and sodium nonylbenzenesulfonic acid;

D. phosphate esters of nonionic surfactants, such as the monoand diphosphate esters of polyoxyethylated dinonylphenol (average 4.5 moles ethylene oxide/mole phenol), potassium salt, as further described in US. Pat. No. 3,352,790;

E. high molecular weight alkyl quaternary ammonium halides, at least one alkyl group preferably containing eight 20 carbons, such as lauryl dimethyl am monium chloride;

F. adducts obtained by reacting from 1-20, preferably 2-10, moles of alkylene oxide such as ethylene or propylene oxide with 1. an alkylphenol; the alkyl radical preferably containing four 18 carbons, such as nonylor dinonyl phenol ethoxylated to an average of 4.5 moles of ethylene oxide/mole of phenol;

2. a high molecular weight alcohol, preferably aliphatic having from six 20 carbons, such as tridecyl alcohol with 9.75 moles ethylene oxide; and

3. a fatty acid, preferably aliphatic having six 20 carbons, such as oleic acid with 15 moles of ethylene oxide;

G. amides of the foregoing adducts such as ethanolamides thereof; and

H. tertiary amide oxides, typically having two lower alkyl radicals (C -C and one saturated or unsaturated alkyl radical of from eight 20 carbons, such as dimethyl hexadecylamine oxide. Often, a number of other ingredients such as lubricants, sweeteners, stabilizers, and the like will be present. Such detergent compositions, or others capable of emulsifying the bleaching solution into the solvent, may be present in the drycleaning system, depending upon a number of variables, within the range of from 0.l-4.0 percent, by volume.

A variety of oxidizing agents have been found useful as bleaching agents when emulsified into the drycleaning solvent system. Included are hydrogen peroxide, the chlorinated cyanouranates, such as sodium dichloroisocyanurate, and, preferably, sodium hypochlorite. Usually these agents are employed as aqueous solutions containing from 3 to 30 percent H 0 or 1 to 5 percent available C1 and are used in the amount of from 0.1 to 6.0 percent by volume of the drycleaning system.

As mentioned, the textile fabrics will generally be subjected to a preliminary drycleaning operation to remove the majority of soils from the fabric, thus reducing the amount of bleach required. Following this, the fabrics will be contacted again with the drycleaning solvent, this time additionally containing the bleaching agent. It will be understood that since water must be present to carry out the bleaching operation, said water generally being provided at least in part by the bleaching solution, and since the fabrics have already been substantially cleaned, the primary purpose of the detergent in the drycleaning system will now be to emulsify the bleaching solution into the solvent, thus providing for efficient contact and bleaching action. While any surfactant capable of emulsifying water in the drycleaning solvent being employed may be used, as a practical matter, the detergent will be the same as that employed in the initial cleaning step. After the fabric has been agitated in the system for a sufficient period of time to effect the desired bleaching action, ten minutes typically sufficing, the neutralizing agent is added, generally as an aqueous solution and in an amount at least sufficient to react with any remaining oxidizing agent. Brief continued agitation is sufficient to complete the neutralization of any excess bleaching agent, following which the solvent may be extracted from the textile fabrics in the usual fashion, said solvent then being passed to the still for recovery. The garments are subsequently dried and deodorized to complete the operation.

The combination of alkali metal sultite and thiosulfate has been found to be singularly effective. Neither however, amounts within the range of to 95 percent have been found effective.

While a wide variety of textile fabrics are subject to the treatment of the present invention, its major application will be in the treatment of cotton and polyesterlcotton blends owing to their wide-spread usage, the susceptibility of the polyester blends to staining and their resistance to shrinking or spotting from the water present in the process.

In order that those skilled in the art may more readily understand the present invention, and certain preferred embodiments by which it may be carried into effect, the following specific examples are afforded.

EXAMPLE 1 The fabric to be treated is a white 65/35 polyester/- cotton blend. In each instance the test fabric is first cleaned by agitation for five minutes in a drycleaning system comprising perchloroethylene, 0.78% by volume water, and 0.13% by volume of a detergent consisting primarily of the potassium salt of an anionic phosphate ester of an ethoxylated dionylphenol (80%) and dimethyl hexadecylamine oxide (20%). Following extraction, the fabric is bleaching again by agitating for five minutes in a system comprising perchloroethylene, 2.9% water, 0.13% of the same detergent, and 9.4% by volume of (5.25% by weight aqueous solution of) sodium hypochlorite. After bleaching, 9.4 milliliters per liter of solvent of an aqueous neutralizing agent solution is added, followed by agitation for five minutes, extraction and drying. The agents employed and results obtained appear in the following Table.

Na sp, 22.1 g/l) ingredient alone is satisfactory. Sodium thiosulfate, for example, while extremely efficient in neutralizing the various bleaching agents, is partially converted to hydrogen sulfide and sulfur dioxide, thereby imparting an extremely undesirable odor to the finished fabric. Sodium sulfite, on the other hand, while imparting no odor to the fabric, is also incapable of effectively neutralizing the bleaching agent. Other compounds, theoretically similar in operation, have been tried but fail, as is shown in the following examples. While the term alkali metal encompasses the usual elements, sodium and potassium are preferred for obvious reasons. The sulfite/thiosulfate mixture is administered, for convenience and to facilitate dispersion and interaction with the bleaching agent, as an aqueous solution containing from 4 percent by weight to saturation, preferably 4 to 35 percent, of the combined salts. Preferably, the major portion, e.g., from 60 to 80 percent, of the combined salts (anhydrous basis) is the alkali metal sulfite,

EXAMPLE 2 Sample 8 of Example 1 is repeated varying the percentage of Na SO at 50, 60, 70, 80, 90, and by weight of the sulfite/thiosulfate mixture. As 50% is approached, sulfurous odors become noticeable. On the other extreme, traces of residual chlorine may be noticed at 95%. Intermediate quantities perform satisfactorily.

EXAMPLE 3 Again repeating Sample 8 of Example 1 but substituting 0.73 milliliters of a 30% aqueous solution of hydrogen peroxide as the bleaching agent, substantially identical results ae obtained.

While the invention has been described with reference to certain preferred embodiments thereof, it is not to be so limited since changes and alterations may be made therein while remaining within the full and intended scope of the appended claims.

I claim:

1. An improvement in the method for bleaching textile fabrics in a drycleaning solvent having emulsified therein an oxidizing agent capable of effecting the desired bleaching, which improvement comprises adding to said solvent, subsequent to completion of the desired bleaching reaction but prior to the removal of the solvent from the textile fabric, a mixture of an alkali metal sulfite and thiosulfate, the alkali metal sulfite constituting from 50 to 95 percent of the alkali metal sulfite/thiosulfate and the amount of said mixture used being at least that sufficient to react with the remaining oxidiz ing agent in the solvent.

2. A method for bleaching textile fabrics which con sists essentially of contacting said fabric with a drycleaning solvent containing an aqueous solution of an oxidizing agent capable of effecting the desired bleaching and a surfactant capable of emulsifying said solution in said solvent followed by adding to the solvent, with agitation, an aqueous mixture of an alkali metal sufilte and thiosulfate, the alkali metal sulfite constituting from 50 to 95 percent of the alkali metal suflite/thiosulfate and the amount of said mixture used being at least that sufficient to react with the remaining oxidizing agent in the solvent.

3. An improvement in the method for bleaching textile fabrics in a drycleaning solvent selected from the group consisting of trichloroethylene, perchloroethylene, and Stoddard solvent containing a solution of an oxidizing agent capable of effecting the desired bleaching and a surfactant capable of emulsifying the oxidizing agent solution in the solvent, which improvement comprises adding to said solvent, subsequent to com pletion of the desired bleaching reaction but prior to removal of the solvent from the textile fabric, an aqueous solution consisting essentially of a mixture of an alkali metal sulfite and thiosulfate, the alkali metal sulfite constituting from 50 to percent of the alkali metal sulfite/thiosulfate and the amount of said mixture used being at least that sufficient to react with the remaining oxidizing agent in the solvent.

4. An improvement in the method for bleaching textile fabrics in a drycleaning solvent having emulsified therein an aqueous solution of an oxidizing agent selected from the group consisting of sodium hypochlorite and hydrogen peroxide, which improvement comprises adding to said solvent, subsequent to completion of the desired bleaching reaction but prior to removal of the solvent from the textile fabric, an aqueous solution of an alkali metal sulfite and thiosulfate, the alkali metal sulfite constituting from 50 to 95 percent of the alkali metal sulfite/thiosulfate and the amount of said mixture used being at least that sufficient to react with the remaining oxidizing agent in the solvent.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,859,044 Dated anuary 7. 1975 lnvent fln) Rodney A. Elgmiield It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 16, "eight 20" should read -8-20-;

line 24, "eight 20" should read -8-20--;

line 34, "eight 20" should read 8-20-;

line 40, 'four 18" should read -4-l8-;

line 44, "six 20" should read --6-20--;

line 46, "six 20" should read --6-20--;

line 53, "eight 20" should read --820-. Column 4, line 26, "bleaching" should read --bleached--;

line 30, before "5.257," insert a-.

Column 5, line 6, "ae" should read are--.

uigned and sealed this lst day of .'=.pril U73.

C. ZLZRSIL'ELL DAB-II? RUTH C. ilASGI-T Commissioner of Patents Lkttestin: Officer and Trademarks FORM USCOMM-DC scan-Pen "-5. GOVIINIINT PRINTING OFFICE 7 I'll 0-3I'3.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,859,044 Dated January 7, 1975 Inven fit) Rodney A. Elgmfield- It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 16, "eight 20" should read 8-20; line '24, "eight 20" should read -8-20--; line 34, "eight 20" should read --820-; line 40, "four 18" should read --4l8--; line 44, six 20" should read -6-20-; line 46, "six 20" should read --6-20--; line 53, "eight 20" should read -8-.-20-. Column 4, line 26, "bleaching" should read --bleached-;

line 30, before "5.25%" insert --a--. Column 5, line 6, "ae" should read -are--.

Signed v sealed this 1st day of 4 1-211 1173.

(S2111, '.ttst:

C. ZLLRSZIALL DAL-3E 313T C. lLkSOI-T Commissioner of Patents Qkttesting Officer and Trademarks FORM PO-1050 (10-69) usco -pc 50315 259 w u.s. Govnunnrr "mums omc: nu 0-306-534. 

1. AN IMPROVEMENT IN THE METHOD FOR BLEACHING TEXTILE FABRICS IN A DRYCLEANING SOLVENT HAVNG EMULSIFIED THEREIN AN OXIDIZING AGENT CAPABLE OF EFFECTING THE DESIRED BLEACHING, WHICH IMPROVEMENT COMPRISED ADDING TO SAID SOLVENT, SUBSEQUENT TO COMPLETIONN OF THE DISIRED BLEACHING REACTION BUT PRIOR TO THE REMOVAL OF THE SOLVENT FROM THE TEXTILE FABRIC, A MIXTURE OF AN ALKALI METAL SLULFITE AND THIOUSULFATE, THE ALKALI METAL SULFITE CONSTITUTING FROM 50 TO 95 PERCENT OF THE ALKALI METAL SULFITE/THIOSULFATE AND THE AMOUNT OF SAID MIXTURE USED BEING AT LEAST THAT SUFFICIENT TO REACT WITH THE REMAINING OXIDIZING AGENT IN THE SOLVENT.
 2. A method for bleaching textile fabrics which consists essentially of contacting said fabric with a drycleaning solvent containing an aqueous solution of an oxidizing agent capable of effecting the desired bleaching and a surfactant capable of emulsifying said solution in said solvent followed by adding to the solvent, with agitation, an aqueous mixture of an alkali metal sufilte and thiosulfate, the alkali metal sulfite constituting from 50 to 95 percent of the alkali metal suflite/thiosulfate and the amount of said mixture used being at least that sufficient to react with the remaining oxidizing agent in the solvent.
 3. An improvement in the method for bleaching textile fabrics in a drycleaning solvent selected from the group consisting of trichloroethylene, perchloroethylene, and Stoddard solvent containing a solution of an oxidizing agent capable of effecting the desired bleaching and a surfactant capable of emulsifying the oxidizing agent solution in the solvent, which improvement comprises adding to said solvent, subsequent to completion of the desired bleaching reaction but prior to removal of the solvent from the textile fabric, an aqueous solution consisting essentially of a mixture of an alkali metal sulfite and thiosulfate, tHe alkali metal sulfite constituting from 50 to 95 percent of the alkali metal sulfite/thiosulfate and the amount of said mixture used being at least that sufficient to react with the remaining oxidizing agent in the solvent.
 4. An improvement in the method for bleaching textile fabrics in a drycleaning solvent having emulsified therein an aqueous solution of an oxidizing agent selected from the group consisting of sodium hypochlorite and hydrogen peroxide, which improvement comprises adding to said solvent, subsequent to completion of the desired bleaching reaction but prior to removal of the solvent from the textile fabric, an aqueous solution of an alkali metal sulfite and thiosulfate, the alkali metal sulfite constituting from 50 to 95 percent of the alkali metal sulfite/thiosulfate and the amount of said mixture used being at least that sufficient to react with the remaining oxidizing agent in the solvent. 